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External Control (§14a EnWG & §9 EEG)

evcc supports external control of charging points and other consumers by grid operators or higher-level energy management systems. The following use cases are supported:

  • §14a EnWG (German regulation): Temporary power reduction and dimming of consumers by the grid operator
  • §9 EEG (German regulation): Curtailment of solar installations in case of grid overload
  • EMS Integration: Applying limits from other energy management systems

Background

Section titled “Background”

Controllable Consumption Devices (§14a EnWG)

Section titled “Controllable Consumption Devices (§14a EnWG)”

§14a of the German Energy Industry Act (EnWG) regulates grid-friendly control of controllable consumption devices (SteuVE). Grid operators can temporarily reduce the power of large consumers such as wallboxes, heat pumps or battery storage systems in the event of grid overload.

Important points:

  • Affects consumers from 4.2 kW power
  • Control via Smart Meter Gateway and control box

Feed-in Management (§9 EEG)

Section titled “Feed-in Management (§9 EEG)”

According to §9 of the Renewable Energy Act (EEG), grid operators can curtail the feed-in of renewable energy installations in the event of imminent grid overload. This mainly affects larger solar installations, but can also become relevant in the residential sector.

Connection Options

Section titled “Connection Options”

Connection is established via Relay (via a switch contact) or EEBus (via the EEBus protocol).

Setup

Section titled “Setup”

Configuration is done via Configuration → External Control. Limits are enforced via Load Management. An “External Limit” circuit (gridcontrol) is automatically created and placed as the top level above any existing circuits.

Configuration via Relay

Section titled “Configuration via Relay”

The connection via a switch contact is the simplest solution. The control box activates a contact which is evaluated by evcc.

Basic Configuration

Section titled “Basic Configuration”
External Control
type: relay
maxPower: 8400 # Total power limit when signal is active (in watts)
limit:
  # Plugin-specific configuration

Determining the Power Limit

Section titled “Determining the Power Limit”

The power limit is communicated to you by the grid operator. For multiple controllable consumption devices (SteuVE), the simultaneity factor is taken into account. You can also calculate the limit yourself using the formula: Total limit = Number of SteuVE × 4.2 kW × Simultaneity factor. Details on the calculation can be found here.

Examples for Different Connections

Section titled “Examples for Different Connections”

When using a Raspberry Pi, the GPIO pin can be read directly:

External Control
type: relay
maxPower: 8400 # Example for 2 SteuVE
limit:
  source: gpio
  function: read
  pin: 17 # Read GPIO pin 17
  # Return value: false = not limited, true = limited

For more details on the GPIO plugin, see the plugin documentation.

Configuration via EEBus

Section titled “Configuration via EEBus”

The digital connection via EEBus is the future-proof and preferred solution. The control box communicates directly with evcc via the EEBus protocol and automatically transmits the power limit.

Prerequisites

Section titled “Prerequisites”
  • Control box with EEBus interface
  • Network connection between evcc and control box

EEBus is preconfigured. The evcc instance’s SHIP-ID and SKI can be viewed under Configuration → EEBus.

Connect Control Box

Section titled “Connect Control Box”

Configure the connection to the control box. You can find the SKI in your control box documentation:

External Control
type: eebus
ski: "1234-5678-90AB-CDEF" # SKI of the control box

Pairing

Section titled “Pairing”

Determine evcc SKI

Section titled “Determine evcc SKI”

The SKI can be viewed under Configuration → EEBus.

Perform Pairing

Section titled “Perform Pairing”

  1. In the control box: Add evcc as HEMS

    • Enter the SKI of evcc
    • Specify the IP address of evcc
    • Start the pairing process

  2. In evcc: Add the control box SKI to the configuration

    • Enter the control box SKI in the configuration
    • Restart evcc

How It Works

Section titled “How It Works”

Normal Operation

Section titled “Normal Operation”

In normal operation, evcc charges without external power limitation. The charging points operate with their normal configuration and are coordinated by additional Load Management restrictions if applicable.

Reduction Signal Active

Section titled “Reduction Signal Active”

When the grid operator sends a reduction signal:

  1. Relay: The contact is closed, evcc activates the configured maxPower limit
  2. EEBus: The control box digitally transmits the calculated total limit

All charging points assigned to the “External Limit” circuit (gridcontrol) are reduced according to the limit. If total consumption is too high, charging processes can also be stopped. The control affects all modes (Solar, Min+Solar, Fast).

Battery control during reduction: If active battery control is configured and grid charging of the home battery is active, this is automatically paused. The battery is set to “hold” mode so that it no longer discharges. Charging the battery from solar surplus is usually still possible. After the power reduction ends, grid charging automatically resumes.

When a control limit is active, a banner with control notice is displayed on the main page in evcc.

Logging

Section titled “Logging”

All limitation requests from the grid operator are automatically documented. The log data can be downloaded as a CSV file under Configuration → External Control.

Each entry contains:

  • Start and end time of the limitation
  • Type of control (consumption reduction or feed-in curtailment)
  • Measured grid power at the start of the limitation
  • Set power limit

This documentation can be provided to the grid operator upon request to verify compliance with control requests.

Controlling Additional Consumers

Section titled “Controlling Additional Consumers”

In addition to charging points, other controllable consumers can also be integrated into German §14a load management. This applies e.g. to heat pumps or battery storage systems that are connected via EEBus or configured as meters with an additional relay output.

The control takes into account the current power consumption of all consumers assigned to the “External Limit” circuit (gridcontrol). This automatically includes all charging points and all meters with corresponding switching outputs or EEBus interface with LPC use case as other consumers.

First, all other consumers are dimmed. The remaining power is then distributed to the active charging points. Due to flat dimming of other consumers, the available charging power for active charging points can in exceptional cases even be higher than in normal state. If throttling the charging points including dimming all other consumers is not sufficient, charging processes at charging points are interrupted.

Further Information

Section titled “Further Information”